Concept:The work function is the threshold energy required to liberate an electron from a metal surface.
Explanation:The work function of a metal is defined as the minimum energy required by an electron to just escape from the metal surface.
It is denoted by
Ï• or
W0​.
When the supplied energy is less than
Ï•, the electron cannot be ejected.
When the supplied energy equals
Ï•, the electron just comes out with zero kinetic energy.
Since this minimum required energy depends on the nature of the metal, it is different for different metals.
Therefore, option B is incorrect because the work function is not equal for all metals.
Options A and D describe maximum energies, which are not correct definitions of the work function.
Answer:Option C: Minimum energy required by an electron to just eject from metal surface.